1. Monoclonal Antibodies Directed Against Cell Membrane Antigens
Monoclonal antibodies (MAbs) to human tumor-associated differentiation antigens offer promises for the "targeting" of various antitumor agents such as radioisotopes, chemotherapeutic drugs, and toxins. [Order, in "Monoclonal Antibodies for Cancer Detection and Therapy", Baldwin and Byers, (eds.), London, Academic Press (1985)].
In addition, some monoclonal antibodies have the advantage of killing tumor cells via antibody-dependent cellular cytotoxicity (ADCC) or complement-dependent cytotoxicity (CDC) in the presence of human effector cells or serum [Hellstrom et al., Proc. Natl. Acad. Sci. USA 83:7059-7063 (1986)], and there are a few monoclonal antibodies that have a direct antitumor activity which does not depend on any host component [Drebin et al., Oncogene 2:387-394 (1988)].
Many monoclonal antibodies reactive with carcinoma-associated antigens are known [see, e.g., Papsidero, "Recent Progress In The Immunological Monitoring Of Carcinomas Using Monoclonal Antibodies, Semin. Surg. Oncol. 1 (4):171-81 (1985); Schlom et al., "Potential Clinical Utility Of Monoclonal Antibodies In The Management Of Human Carcinomas", Important Adv. Oncol., 170-92 (1985); Allum et al., "Monoclonal Antibodies In The Diagnosis And Treatment of Malignant Conditions", Surg. Ann., 18:41-64 (1986); and Houghton et al., "Monoclonal Antibodies: Potential Applications To The Treatment Of Cancer", Semin. Oncol., 13(2):165-79 (1986)].
These known monoclonal antibodies can bind to a variety of different carcinoma-associated antigens including glycoproteins, glycolipids and mucins [see, e.g., Fink et al., "Monoclonal Antibodies As Diagnostic Reagents for The Identification And Characterization Of Human Tumor Antigens", Prog. Clin. Pathol. 9:121-33 (1984)].
For example, monoclonal antibodies that bind to glycoprotein antigens on specific types of carcinomas include those described in U.S. Pat. No. 4,737,579 (monoclonal antibodies to non-small cell lung carcinomas), U.S. Pat. No. 4,753,894 (monoclonal antibodies to human breast cancer), U.S. Pat. No. 4,579,827 (monoclonal antibodies to human gastrointestinal cancer), and U.S. Pat. No. 4,713,352 (monoclonal antibodies to human renal carcinoma).
Monoclonal antibody B72.3, which is one of the antibodies studied the most, recognizes a tumor-associated mucin antigen of greater than 1,000 kd molecular weight that is selectively expressed on a number of different carcinomas. Thus, B72.3 has been shown to react with 84% of breast carcinomas, 94% of colon carcinomas, 100% of ovarian carcinomas and 96% of non-small cell lung carcinomas [see Johnston, "Applications of Monoclonal Antibodies In Clinical Cytology As Exemplified By Studies With Monoclonal Antibody B72.3", Acta Cytol., 1(5): 537-56 (1987) and U.S. Pat. No. 4,612,282, issued to Schlom et al.]. Another patented monoclonal antibody, KC-4, [see U.S. Pat. No. 4,708,930], recognizes an approximately 400-500 kd protein antigen expressed on a number of carcinomas, such as colon, prostate, lung and breast carcinoma. It appears that neither the B72.3 nor KC-4 antibodies internalize within the carcinoma cells with which they react.
Monoclonal antibodies reactive with glycolipid antigens associated with tumor cells have been disclosed. For example, Young et al., "Production Of Monoclonal Antibodies Specific For Two Distinct Steric Portions Of The Glycolipid Ganglio-N-Triosylceramide (Asialo GM.sub.2)", J. Exp. Med., 150: 1008-1019 (1979) disclose the production of two monoclonal antibodies specific for asialo GM.sub.2, a cell surface glycosphingolipid antigen that was established as a marker for BALB/c V3T3 cells transformed by Kirsten murine sarcoma virus. See, also, Kniep et al., "Gangliotriasylceramide (Asialo GM.sub.2) A Glycosphingolipid Marker For Cell Lines Derived From Patients With Hodgkin's Disease", J. Immunol., 131(3): 1591-94 (1983) and U.S. Pat. No. 4,507,391 (monoclonal antibody to human melanoma).
Other monoclonal antibodies reactive with glycolipid antigens on carcinoma cells include those described by Rosen et al., "Analysis Of Human Small Cell Lung Cancer Differentiation Antigens Using A Panel Of Rat Monoclonal Antibodies", Cancer Research, 44:2052-61 (1984) (monoclonal antibodies to human small cell lung cancer), Varki et al., "Antigens Associated with a Human Lung Adenocarcinoma Defined by Monoclonal Antibodies", Cancer Research 44:681-87 (1984); (monoclonal antibodies to human adenocarcinomas of the lung, stomach and colon and melanoma), and U.S. Pat. No. 4,579,827 (monoclonal antibodies to human colon adenocarcinoma). See, also, Hellstrom et al., "Antitumor Effects Of L6, An IgG2a Antibody That Reacts With Most Human Carcinomas", Proc. Natl. Acad. Sci. USA, 83:7059-63 (1986) which describes the L6 monoclonal antibody that recognizes a carbohydrate antigen expressed on the surface of human non-small cell lung carcinomas, breast carcinomas and colon carcinomas.
Antibodies to tumor-associated antigens which are not able to internalize within the tumor cells to which they bind are generally not useful to prepare conjugates with antitumor drugs or toxins, since these would not be able to reach their site of action within the cell. Other approaches would then be needed so as to use such antibodies therapeutically.
Additional monoclonal antibodies exhibiting a high specific reactivity to the majority of cells from a wide range of carcinomas are greatly needed. This is so because of the antigenic heterogeneity of many carcinomas which often necessitates, in diagnosis or therapy, the use of a number of different monoclonal antibodies to the same tumor mass. There is a further need, especially for therapy, for so called "internalizing" antibodies, i.e., antibodies that are easily taken up by the tumor cells to which they bind. Antibodies of this type find use in therapeutic methods for selective cell killing utilizing antibody-drug or antibody-toxin conjugates ("immunotoxins") wherein a therapeutic antitumor agent is chemically or biologically linked to an antibody or growth factor for delivery to the tumor, where the antibody binds to the tumor-associated antigen or receptor with which it is reactive and "delivers" the antitumor agent inside the tumor cells [see, e.g., Embleton et al., "Antibody Targeting Of Anti-Cancer Agents", in Monoclonal Antibodies For Cancer Detection and Therapy, pp. 317-44 (Academic Press, 1985)].